jsmith24

Hi guys,

At 2500 rpm or so I get a noise that sounds like valve train rattle. When I took the car in today to get the camshaft recall done, the tech diagnosed it as "spark rattle", probably due to bad/low octane gas. I told him I've always used 93 octane, and it's been doing it for the last 8-10 tanks, using different gas brands.

So, is this total BS? Will the valves rattle on our engines? I seem to remember reading that the new valve setup virtually eliminates that. I didn't really argue with the dealer/tech because I don't have all the facts....can anyone give me more info?

Thanks,

Jack
2003 Max
6 speed HLSD

Jeff92se

iTrader: (82)

It's called "detonation" or "ping". It's not normal. Ask to drive another 2003 on the lot and see if that has "spark rattle". It probably will not.

MiniRX7

Interesting I HAVE THE EXACT SAME THING on my 2k3.... and its not detonation or pining.. I know it sounds like pure rattline especially on deceleration.

Can you explain your problem a little more detailed?

hotrod37

If it is in fact spark rattle which is quite common if it is hot and your gas is not of a good grade. YOu may be paying for 93 but who knows what is actually comming out of the pump. Gas stations have been know to put 87 oct gas in the 93 tanks.

But back to the point You will not get spark rattle while the car is decelerting if you hear the noise then my guess would be valve train.

jsmith24

I should have elaborated...

My car makes this rattling noise while accelerating, and is a little more prominent going uphill. To the best of my experience, it doesn't sound what I think "ping" or detonation would sound like. It sounds like the worn valves in my moms old '86 Pontiac.

After my service today, the car seemed "newer", seemed to pull just a bit stornger. I didn't notice the rattling sound, but I didn't drive very far. I will update Monday after my holiday trip.

Thanks for the replies, too. I always feel that I can ask stupid questions here without too much ribbing.

Jack

paralyse

Fairly easy to check -- Take a metal rod or mechanic's stethoscope and listen to the valves on both heads while the engine is running, and have someone rev it. Detonation or knocking usually only occur under load and commonly get worse under heavier loads, such as going up hills!

If you've kept up on your oil changes I highly doubt you have a valvetrain issue.

The fact that you said it gets worse going up hills would make me think it's spark knock.

If you have access try a bottle of 104+ Octane boost or NOS Octane Booster or anything else that says "for off-road use only" and see if it makes any difference at all.

2002 Maxima SE

iTrader: (3)

I have this while decelerating...but it is very, very faint. Usually around 2000 to 2500 rpm from 35mph to 45mph. Surprisingly, it is more prominent when decelerating down a hill with light throttle.